1. Field of the Invention
This invention relates to a vibration testing apparatus.
2. Prior Art
A conventional vibration testing apparatus is described, for example, in Japanese Laid-open Patent Publication No. 152,580/1987. In this apparatus, X-direction and Y-direction connection elements in a hollow portion of a vibration section each have a multi-sided cross section. Each connection element has a pressure-receiving surface parallel and opposite an inner surface of the hollow portion. A pair of pressure-receiving plates, parallel and opposite to a pair of pressure-receiving surfaces, cooperate to define a space, which may be used as a static pressure bearing. A plurality of connecting members interconnect the pressure-receiving plates. A vibration generator is connected to the pressure-receiving plates by a stiff transmission member that extends through the vibration section. Oil is pumped into the space under pressure, creating a firm but somewhat resilient connection between the pressure-receiving plates and the transmission member. Thus the static pressure bearings transmit vibration from the vibration generator to the vibration section.
In this prior-art vibration testing apparatus, the connecting members must have sufficient strength to support all the forces that act in the directions of vibrations. Therefore the connecting members must necessarily be very large. Further, since the connecting members in X- and Y-directions must vibrate independently of each other while maintaining the same strength, their arrangement is complicated. A plurality of alternating connecting members must be employed, making assembly of the apparatus difficult.
Another drawback of the prior-art apparatus is that, since it has no means to correct the gap in the static pressure bearing when it changes due to changes in temperature, the static pressure bearing has to be assembled with a large gap distance. Though the large gap distance allows for such changes, it makes increasing the rigidity of the bearing difficult.